Temperature control system



Aug, 13 1940.

Filed Sept. 9, 19:57

- l 4-HO 50 133 INVENTOR Henrg E- Harfi ATTORNEY Patented Aug. 13, 1940 UNITED STATES PATENT OFFICE Minneapolis-Honeywell Regulator Company,

Minneapolis, Minn., a corporation of Delaware Application September 9, 1937, Serial No. 163,052

3 Claims.

This invention relates to a temperature control system and while I have illustrated it in connection with a heating system, it should be understood that it is equally applicable to a cooling 5 system.

In a conventional type of a modern heating system, a heater is controlled by a space thermostat to maintain the temperature of the space being heated within certain predetermined limits.

10 One of the defects of such a system is due to the time lag that necessarily exists between the time the space thermostat calls for more heat and the time that the heat arrives in the space being heated. The effect of a rise in temperature in 5 the heater is not felt in the space being heated for a considerable time, and as a result, the temperature in the space may continue to fall for an appreciable time after the thermostat calls for heat, before the temperature starts to rise again,

90 thus causing physical discomfort to the occupants of the space.

It is well known that a change in temperature in the atmosphere surrounding a building is not felt within the building for a considerable time 25 because of the insulating properties of the walls. This knowledge is utilized to advantage in my system to anticipate a change in temperature in the space being heated so that the temperature of the heater is raised before actual additional heat 9 is required in the space, but at such a time that additional heat will be furnished to the space at the same time as the drop in outside temperature makes its effect apparent in the space.

One way of accomplishing this is by placing a 35 temperature responsive device in a wall of the space, at such a point in the wall that the time required for a change in temperature at this pointto affect the temperature of the space is the same as the time required for the change in tempera- 40 ture in the heater to affect the temperature of the space. Fuel is continuously supplied to the heater, and a valve regulates the amount of fuel being supplied, this valve being controlled by the aforementioned temperature responsive device so 45 that the correct amount of fuel is being continuously supplied tomaintain a substantially uniform temperature. Additional controlling means for the fuel are provided to compensate for abnormal conditions affecting the temperature of the space which conditions can not be effectively controlled by the temperature responsive device in the Wall.

It is therefore an object of my invention to pro- 55 vide an improved control means for a temperature changing system by which the temperature of a space is maintained at a constant value.

A further object of my invention is to provide means for compensating for the effect of the time lag of a temperature changing device on a space being controlled thereby.

More specifically, it is an object of my invention to provide a temperature changing system wherein a temperature changing device is provided for controlling the temperature of a space, and wherein a temperature changing medium is continuously supplied to said device in varying amounts in accordance with outside temperature changes, and wherein the amount of the temperature changing medium being supplied is varied in advance of a call for more or less heat in the space so that the amount of heat reaching the space is varied at the same time that the effect of the changing outdoor temperature is felt in the space.

Other objects will become apparent upon a study of the specification, claims, and appended drawing, wherein is schematically illustrated a preferred form of my invention.

Referring to the drawing, a heater W is provided which may be a gas fired hot water furnace, for example. For supplying gas to the furnace i 0,

a pipe line H is provided, said pipe line being controlled by valves [2 and [3. A pipe i4 shunts the valve l3 and is in turn controlled by avalve I5. A pipe line i6 constantly supplies fuel to a suitable pilot (not shown) for insuring the ignition of the gas issuing from the burner (not shown) in furnace ll]. Pipes I7 and I8 connect the furnace Hi to a radiator 3! located in the space being controlled.

Valve [2 comprises a body 20 and a valve element shown at 2| which, as is shown, is normally in wide open position. Extending upwardly from the valve element 2i is a valve stem 22 connected with an armature 23 which is in turn surrounded by a solenoid 24. Energization of solenoid 24 causes armature 23 and valve element 2| to moveupwardly into a position in which the flow of fuel to the furnace I0 is out 01f entirely. Valve I5 comprises a valve body 26 and a valve element 21 which is normally in closed position. Extending upwardly from the valve element 21 is a valve stem 28 to which is connected an armature 29 surrounded by a solenoid 30, energization of which causes armature 29 and valve element 26 to move into open position. With both valves l5 and 20 in open position, valve [3 exercises no control over the supply of fuel to the furnace l0 and the supply of fuel is at a maximum. 55

Valve I3 is provided to regulate the amount of fuel which may pass to the furnace I0 when valves I2 and I5 are in their normal positions as illustrated.. To valve I3 is connected a stem 32, which stem is connected by means of a link 33 to a crank member 34. With the crank in the position illustrated, valve I3 is in mid position permitting the fuel to be supplied to the furnace I0 at approximately 50% of the maximum capacity of the furnace.

A section of an outside wall of the space being heated is represented by the reference character 40 and positioned'in said space is a tube 4| which communicates with an expansible bellows 42. Tube 4| is filled with an expansible fluid which expands or contracts in response to temperature changes so that a change in temperature at the point where the tube 4| is located will cause a change in pressure in bellows 42 causing said bellows to expand or contract according to whether the temperature surrounding the tube 4| has increased or decreased.

A motor generally indicated by the reference character 50 is provided for causing operation of crank member 34 and the adjustment of valve I3. type and comprises an armature 5|, field coils 52 and 53, and a condenser 54. Field windings 52 and 53 are connected together at one end thereof and between the opposite ends of said windings is connected the condenser 54. The junction of windings 52 and 53 is permanently connected to the low tension secondary 55 of a step-down transformer 56, the high tension primary 51 of said transformer being connected by means of conductors 58 and 59 to lines I00 and IOI which are in turn connected to a suitable source of power (notshown) Condenser 54 may be selectively connected between either winding 52 or 53 to the other side of the transformer secondary 55, and the other winding is directly connected to said other side of the transformer secondary 55. The current through the winding which is in series with condenser 54 leads the current through the other winding in phase and thus the direction of rotation of armature 5| may be controlled by changing the winding in series with said condenser.

A relay generally indicated by the reference character 60 is provided for changing the phase relationship of windings 52 and 53. This relay is of the balanced type and comprises opposed windings 6| and 62, an armature 63 connected to a switch arm 64, said arm cooperating with fixed contacts 65 and 66. Windings 6| and 62 are connected together at one end, the opposite end of winding 6| being connected to the transformer secondary 55 by means of conductors I0 and II and the other end of coil 62 being connected to the opposite side of the transformer secondary 55 by means of conductors I2 and I3. Connected in parallel with the coils 6| and 62 is a potentiometer resistance I5 of a potentiometer I4, said resistance being connected to the coils by means of protective resistances I6 and II. A. potentiometer arm I8 is arranged to sweep across the resistance I5, this arm being connected by means of a link I9 to the bellows 42 to be actuated thereby. t A second potentiometer resistance of a potentiometer 86 is connected by means of conductors 8| and 02 in parallel with the potentiometer resistance I5 and therefore to the relay coils 6| and 62. An arm 93 is arranged to sweep across resistance'80, this arm being mounted on This motor is of the condenser induction a shaft 84 which is connected by means of a reduction gearing 85 to the armature 5| of motor 50 for rotation thereby. Shaft 84 also carries the crank 34 for rotation therewith and also carries an insulated arm which cooperates with switches 9| and 92, switch 9| including contact elements 93 and 94 and switch 92 including contact elements 95 and 96.

Arms I8 and 83 of potentiometersM and 86, respectively, are connected together by means of conductors I02 and I03 and these arms are also connected to the junction of coils 6| and 62 of relay 60 by means of conductors I02, I03, and I04, as illustrated. Potentiometer I4 is a controlling potentiometer and acts as a voltage divider for coils 6| and 62. With arm I8 in the mid position, as shown, disregarding for the moment potentiometer 86, it will be apparent that the current through coils 6| and 62 is equal so that these coils have no effect on armature 63 and it remains in the mid position as illustrated.

Movement of arm I8 to the right will cause the current through coil 6| to become greater than that through coil 62, thus causing armature 63 to move to the left, and conversely, movement of the arm I8 to the left causes relay coil 62 to become more highly energized than coil 6| whereupon the armature 63 moves to the right,

switch arm 64 being moved by armature 63 into engagement with either contacts 85 or 66, depending upon which relay coil is the more highly energized. Potentiometer 86 is a balancing potentiometer and is designed to balance the effect of potentiometer I4. Thus as arm I8 of potentiometer I4 is moved to the right, movement of arm 03? of potentiometer 86 to the left a corresponding amount will neutralize the effect of potentiometer I4 on relay 60.

Resistances I6 and II are for the purpose of preventing a short circuit across the transformer secondary should the arms I8 and 83 reach their extreme positions so that current does not have V to flow through the potentiometer resistances I5 and 80. Switches 9| and 92 are provided between the field windings 53 and 52, respectively, and the source of power, and are opened upon sulficient movement of the arm 90 in either direction so as to prevent rotation of crank member 34 beyond a predetermined point by the motor 50.

Mounted in the space being heated is a thermostat IIO, said thermostat comprising a bimetallic element I I I, a blade I I2 connected thereto for movement thereby in response to temperatu're changes in the space H0 and fixed contacts H3 and H4 for cooperation with blade II2.

For controlling the current through solenoid 24 is a relay indicated generally by the reference character II6, this relay comprising a coil III,

an armature I I8, switch blade I I 9, and a fixed contact I20. Energization of solenoid 30 is controlled by a relay I22 which relay comprises a relay coil I23, an armature I24, a switch blade I25 and a fixed contact I26 cooperating therewith. These relays are controlled by thermostat I I0 as will be hereinafter pointed out. For energizing said relays a transformer I30 is provided, said transformer including a low tension secondary I3I and a high tension primary I 32, said primary being connected across the lines I00 and IOI by means of conductors I33 and I34.

With the parts in the position illustrated, valve I3 is in mid positiorin which it is supplying about 50% of the maximum capacity of the burner I0. Valve I2 is in its normal open position and valve I5 is in its normal closed position. Thermostat I I is in mid position in which position it is neither calling for more nor less heat.

The tube 4| is located a sufficient distance from the inside wall surface of the space being heated so that a change in temperature at this point will take the same length of time to effect the temperature of the space as will a change in the flow of gas to furnace I0 take to affect the temperature of the space.

Operation Assume that the outside temperature begins to fall. This will not have any effect on the temperature of the space until a considerable time elapses. After a certain length of time, the temperature of the wall at the point at which tube 4| is located will decrease causing a contraction of bellows 42 whereupon the arm I8 of potentiometer I5 will move to the left an amount which is in proportion to the amount of fall in temperature at the aforementioned point in said wall. Movement of arm I8 to the left will cause relay coil 62 to become more highly energized than coil 6| whereupon the armature 63 will I move to the right causing switch arm 64 to move into engagement with contact 66. now be energized through the following circuits: from the secondary 55 of transformer 56, through conductors I3, I40, switch blade 64, contact 66, conductor |4|, switch elements 95 and 96, conductor I42 through field winding 52 and through conductors I43 and II to the other side of the transformer secondary 55. Current also flows through the field winding 53 as follows: from the secondary 55 through conductors I3, I40,

switch blade 64, contact 66, conductor I, switch elements 95, 96, conductors I42, I44, through the condenser 54, conductor I45 through field winding 53 and conductors I43 and H to the other side of secondary 55. Current through winding 53 leads that through Winding 52 in phase and the armature rotates in a clockwise direction causing crank 34 to move in the same direction. Potentiometer arm 83 is moved to the right, and the motor armature 5| continues to rotate until arm 83 has moved a distance which is sufficient to balance the effect of potentiometer I5 on coils 6i and 62 of relay 60. When this happens, coils 6| and 62 again become equally energized, whereupon armature 63 moves back to mid position causing switch blade 64 to also move to mid position. Crank 34 has now caused valve |3 to open an amount which is in proportion to the fall in temperature at the point in wall 40 where tube 4| is-located. The amount of fuel supplied to furnacelO is accordingly increased. After a sufficient time elapses the effect of this increase in fuel delivery will be apparent in the space being heated. At the time that the effect of the increased fuel supply is felt in the space being heated, the effect of the lowered temperature on the outside of wall 40 will also be felt in the room so that the increase in fuel delivery will just compensate for the lowered outside temperature and will become effective at the time that additional heat will be required in the space. It will, therefore, be seen that a fall in temperature in the room occasioned by a decrease in outdoor temperature is anticipated by the heater before the lowered outdoor temperature actually affects the temperature of the room.

Should an abnormal condition cause a rapid lowering of the temperature in the space, such as the opening of a window or a door, the temperature responsive member 4| will be ineffective to Motor 50 will cause an immediate increase in the flow of fuel to the burner. The bimetallic element III of room thermostat III! will cause arm H2 carried thereby to be moved to the left in response to this decrease in temperature, into engagement with contact 3. Relay coil I22-will now be energized through the following circuit: from transformer secondary |3|, through conductor I50, the bimetallic element arm 2, contact ||3, conductor |5|, relay coil I23, and conductor I52 to theother side of secondary |3|. Energizetion of coil I23 causes switch blade I25 to move into engagement with contact I26 whereupon solenoid 30 is energized through the following circuit: from line I00 through conductors I55, I56, switch blade I25, contact I26, conductor I5! through the solenoid 30 and conductors I58 and I59 to the line |0|. Energization of solenoid 30 causes armature 29 and valve element 21 to be moved upwardly, whereupon fuel may flow through the valve I5 and pipe line I4 to the burner I0. the valve l3 and the amount of fuel being delivered to the furnace I0 is at a maximum. The temperature in the space will accordingly begin to rise after a certain time, and after a certain length of time thermostat I|0 will become satisfied and blade I|2 will be moved to mid position by the bimetallic element III, whereupon relay I22 will be dee-nergized, in turn causing solenoid '30 to become deenergized. whereupon the valve 2'! moves back to closed position and the furnace I0 is again under the control of valve I3.

Should the temperature in the space for some reason rise to a certain high value, it will be desirable to stop the supply of fuel to the furnace I0. The attainment of this high temperature will result in bimetallic element III moving the thermostat blade I I2 into engagement with contact H4 and energizing relay coil III through the following circuit: from the low tension secondary I3| of transformer I30, through conductor I50, bimetallic element III, arm ||2, contact H4. conductor I60, through coil Ill and conductors IM and I52 to the other side of secondary I3I. Switch blade 9 is now caused to move into engagement with contact I20 whereupon solenoid 24 is energized through the-following circuit: from line I00, through conductors I55, I62, switch blade II9, contact I20, conductor I63, through solenoid 24 and'conductors I64 and I59 to the line IOI. Energization of solenoid 24 causes valve element 2| to move upwardly into a position in which the supply of fuel to furnace I0 is cut off entirely. This situation will exist until the temperature of the space being heated falls to av desired value whereupon the arm 2 moves out of engagement with contact 4 thus causing relay coil II! to become dcenergized which results in the deenergization of solenoid 24. Valve 2| now moves back toits normally open position whereupon furnace I0 is placed under control of valve I3.

Should the outside temperature continue to drop, it will be apparent that after a certain time elapses bellows 42 will be further contracted moving arm I8 further to the left causing a corresponding rotation of motor armature 5| and crank member 34 until the effect of potentiometer I4 is again neutralized by the movement of arm 63 further to the right over potentiometer 86.

Assume now that the outdoor temperature begins to rise after a certain period of time. This increase in outdoor temperature will be felt by the tube 4| whereupon the fluid therein expands Thus the fuel is allowed to by-pass' causing expansion of bellows 42 which will cause arm I8 to move towards the right, whereupon the relay coil 6| will become more highly energized than coil 62 and armature 63 will move toward the left moving with it switch arm 64 into engagement with contact 65. Motor 50 will now be energized through the following circuit:- from transformer secondary 55, through conductors I3, I40, switch blade 54, contact 65, conductor I'Ill, switch elements 94 and 93, conductor I'II through Winding 53 and conductors I43 and II to the other side of secondary 55. Current also flows through field winding 52 as follows: from the secondary 55- through conductors I3, I40, switch blade 64, contact 65, conductor I10, switch elements 94 and 93, conductors Ill and I45, condenser 54, conductor I44, field winding 52 and conductors I43 and II to the other side of secondary 55. The current through winding 52 now leads the current through winding 53 in phase and causes armature 5I to move in a counter-clockwise direction, which in turn causes crank element 54 to move in a'clockwise direction, thus moving valve I3 towards closed position. This movement will continue until arm 83 which is being moved to the left over resistance has moved far enough to counteract the effect of potentiometer I5 on the relay coils GI and 62, whereupon armature 63 and switch blade 64 will move back to their mid positions causing deenergization of motor 50.

The amount of fuel now passing through valve I3 has been reduced just enough to compensate for the increase in the outdoor temperature so that when the increase is felt in the space being heated, the decrease in heat delivery to said space will also be decreased to just compensate for the increase in the outdoor temperature.

It will thus be seen that when no abnormal conditions affect the temperature of I the space being heated, that the fuel delivery to the heater will automatically be adjusted in. accordance with changes in the outdoor temperature at the proper time so that when the effect of the outdoor temperature change would be felt in the space being heated the corresponding change in the fuel supply to the furnace will be effective at the same time. Therefore, under normal conditions in which changing outdoor temperatures are the only elements affecting the temperature of the space, a substantially constant temperature will at all times be maintained in the space. However, should abnormal conditions arise causing a raising or lowering of the space temperature above or below the desired values, thesupply of fuel to the burner will immediately be reduced or increased according to whether the temperatures are too high or too low. I

'This system, of course, would be just as applicable to a cooling system in which a cooling medium was being supplied to a device for the purpose of maintaining a predetermined low temperature during the summertime as it is to a heating system. It will also be obvious that the system is equally applicable to one using other types of fuel than gas for the heating medium. It would also be useful in other types of heating systems, such as a hot air heating system, having a shorter time lag than a hot water system. In such a. system, tube 4| would, I

of course, be placed nearer the inside of wall 40 since it has to compensate for a shorter time lag.

of said medium through said conducting means,

a second valve means controlling the flow of said medium to said device, temperature responsive means responsive to the temperature at a point in a wall of a space whose temperature is being controlled, in control of said first valve means, said point being so located that the time required for a change in temperature at said point to affect the temperature of said space is L approximately equal to the time required for operation of said first valve means to affect the temperature of said space, space temperature responsive means in control of said second valve means whereby the second valve means cuts off the supply of the temperature changing medium in response to the attainment of one predetermined temperature and causes maximum flow of said medium in response to the attainment of a second predetermined temperature in said space.

2. In a temperature control system, a temperature changing device for controlling the temperature of a space, means for conducting a temperature changing medium to said device, said means comprising a pipe including a main line and a pair of branch lines, a normally open valve in said main line, a normally closed valve in one of said branch lines, an adjustable valve in said other branch line, temperature responsive means located Within the outside wall of the building for controlling the position of said adjustable valve in accordance with the temperature within said outside wall, means responsive to the attainment of one undesirable temperature in said space for opening said normally closed valve, and means responsive to the attainment of another undesirable temperature in said space for closing said normally open valve.

3. In a temperature control system, a temperature changing device for controlling the temperature of a space, means for conducting a temperature changing medium to said device, said means comprising a pipe including a main line and a pair of branch lines, a normally open valve in said main line, a normally closed valve in one of said branch lines, an adjustable valve in said other branch line, temperature responsive means located within the outside wall of the building for controlling the position of said adjustable valve in accordance with the temperature within said outside wall, said temperature responsive means being so located within said wall that the time required for a change in temperature at said point to affect the temperature of said space is substantially equal to the time required for a change in the position of said adjustable valve to affect the temperature of said space, means responsive to the attainment of one undesirable temperature in said space for opening said normally closed valve, and means responsive to the attainment of another undesirable temperature in said space for closing said normally open valve.

HENRY E. HARTIG. 

